* {
  margin: 0;
  padding: 0;
}
#demo {
  width: 3.45rem;
  height: 1.5rem;
  background-color: skyblue;
  margin: 0 auto;
  margin-top: 0.15rem;
  /* border: 0.01rem solid black; */
  border: 1px solid black;
}
